The invention relates to a gas stream monitor that automatically shuts off gas conduits in the event of an inadmissible flow increase as specified in the introductory clause of the first patent claim.
Such gas stream monitors, employed in pipelines, e.g. upstream of gas valves, gas appliances, etc., are available in a large variety of designs. Their purpose is to discontinue gas supply if gas consumption exceeds a predefined value.
WO 92/01184, for instance, describes a gas stream monitor of the above-mentioned type which shuts a pipe system in case of damage but does not effect a premature shutting off of the supply line if a consumer requires the gas volume corresponding to its rated output over a longer period. One valve in this so-called safety shut-off mechanism is designed as a disk valve.
The set-up of this valve is as follows: the valve body is fixed to a valve shaft that is movably arranged on either side in slide bearings in axial valve direction and opposing the force of a spring. The valve disk is jointly acting with a valve seat supported by two flat rings which simultaneously serve as joints for the above-mentioned slide bearings. The flat rings are provided with cut-outs or breakthroughs.
The springiness of the spring and/or the reseating path of the valve are adjustable in order to exactly adapt the reseat flow to the type, nature and number of consumers. A nut is provided at the free end of the valve shaft for the adjustment of the reseating path of the valve, the nut is screwed to a thread on the valve shaft An adjusting device, e.g. a second nut between the two slide bearings, is provided to adjust the springiness.
An automatic shut-off valve is also known from GB Patent 556,863. This shut-off valve consists of a tubelike casing with threaded connections on either side. The casing is fitted with a flat ring with breakthroughs, which ring has at its centre a slide bearing for a longitudinally moving valve shaft with a valve gate at its end which acts together with a valve seat in the casing. A pressure spring, that is supported on one side by the valve gate and at the other by the flat ring, keeps the valve gate in the open position until the adjusted reseat flow is achieved. Also in this design the reseat flow is changed by a modification of the springiness adjustment by altering the tap depth of the valve shaft into a hood, and thus the installation length of the spring.
A valve described in U.S. Pat. No. 3,794,077 has a similar set-up. A pressure spring, with breakthroughs, supported on one side by a slide bearing at the casing and on the other by a nut screwed to the valve shaft keeps the valve gate in the open position until the adjusted reseat flow is achieved. Also there, a changing of the nut position, which is secured against turning with a pin, on the valve shaft the installation length of the pressure spring is altered and thus the reseat flow altered by a change of the springiness.
The disadvantage of all those solutions is that the reseat flow can only be adjusted by interior manipulations of the gas stream monitor and, hence, respective provisions have to be made already during manufacturing. This means, however, that already then the specific application, i.e. the technical parameters of the consumers downstream of the place of installation, have to be known. This is the reason why there are specific gas stream monitors available for each application.
The following happens in the known gas stream monitors: after a shut-off due to gas consumption in excess of the reseat flow, caused e.g. by a damaged gas conduit or a defective consumer, the gas stream monitor is re-opened after defect remediation by building up pressure on the consumer side until the valve disk is lifting from the valve seat and thus the flow cross-section is released again. This procedure, however, is often very time-consuming.
An overflow aperture in the valve disk is another possibility where, following the remediation of the defect and shutting of all consumers, the overflow aperture facilitates a pressure build-up in the consumer-side gas conduit until pressure compensation is reached and the gas stream monitor re-opens. The disadvantage is that, in an emergency case, a certain volume of leaking gas flows through the gas stream monitor even after it has been shut.
The invention is focusing on the issue of developing a gas stream monitor of the described type in which the adjustment/alteration of the reseat flow can also be made after its manufacturing. In particular, it should also be possible to change the reseat flow after the valve has been installed. According to the present invention the problem is solved by means of a gas stream monitor, consisting of a gas-tight casing, internally equipped with a seat for a reseating body that is movable inside the casing and is kept in the open position against the flow direction by its own weight and/or springiness, and where the flow cross-section, the surface of the reseating body and the forces are determined in such a manner that the gas stream monitor laves its open position upon a defined value of the reseat flow and is moved towards the casing seat so that the gas conduit is shut in the shut position, and that has, outside of the casing, at least a manipulator in the form of a tappet leading into the casing interior to adjust the spring pre-tension and/or the stroke of the reseating body.
Thus, a solution has been found that abolished the disadvantages of the prior art where the adjustment of the reseat flow was only possible by interference in the interior of the gas stream monitors, which is now already provided for during manufacturing.
Further advantageous arrangements of the invention are described in the other patent claims. It is, e.g., possible to arrange two or more reseat bodies in parallel inside the casing, each of which reseat bodies being assigned with a manipulator with a tappet leading into the casing interior to facilitate the adjustment of the spring pre-tension and/or the stroke of the reseat body.
It is particularly advantageous when the manipulator to adjust the pre-tension and/or the stroke of the reseat body can also be used to adjust the shut position of the reseat body. Thus, it is possible that this gas stream monitor can additionally act also as a shut-off valve.
Favourably for the adjustment/alteration of the reseat flow of the gas stream monitors the manipulator is supported by a sliding block which, e.g., can be equipped with lock-in positions for preferential values of the reseat flow.
A further arrangement of the invention is that the reseat body in the shut position can be moved out of the shut position by means of a key button operable from outside. Thus it is possible, following the remediation of the defect and shutting of all consumers, to initiate a pressure build-up in the consumer-side gas conduit until pressure compensation is achieved and the gas stream monitor remains open. An overflow aperture is not necessary and thus a gas-tight closure possible.
Particularly favourable is the embodiment in which the slide block has a control slope and the tappet is simultaneously interlocked with the reseat body shaft that, upon actuation of the manipulator, the reseat body is movable from its shut position by means of the control slope and the manipulator automatically leaves the range of action of the control slope. This solution does not require a separate key button since the key button function is integrated into the manipulator. Also the otherwise required through boring in the casing is not necessary.
In order to change the adjusting value of the reseat flow the reseat stroke can be altered in the place of a springiness alteration. This is possible since the connection between manipulator and tappet is adjustable, i.e. the insert or thread depth of the tappet can be altered.